For many applications (most of which are Windows ones) there are neither sources nor tarballs available. Many of such applications can not be freely distributed because of license restrictions and/or lack of legal ways to obtain installer for no fee. Such software obviously can not be included into the official repositories but due to nature of AUR it is still possible to privately build packages for it, manageable with pacman.

Note: All information here is package-agnostic, for information specific to the most typical nonfree software see Wine PKGBUILD guidelines.

Rationale

There are multiple reasons for packaging even non-packageable software:

Simplification of installation/removal process

This is applicable even to the simplest of apps, which consist of a single script to be installed into /usr/bin. Instead of issuing:

$ chmod +x filename

# cp filename /usr/bin/

you can type just

# makepkg -i

Most non-free applications are obviously much more complicated, but the burden of downloading an archive/installer from a homepage (often full of advertising), unpacking/decrypting it, hand-writing stereotypical launcher scripts and doing other similar tasks can be effectively lightened by a well-written packaging script.

Utilizing pacman capabilities

The ability to track state, perform automatic updates of any installed piece of software, determine ownership of every single file, and store compressed packages in a well-organized cache is what makes GNU/Linux distributions so powerful.

Sharing code and knowledge

It is simpler to apply tweaks, fix bugs and seek/provide help in a single public place like AUR versus submitting patches to proprietary developers who may have ceased support or asking vague questions on general purpose forums.

Common rules

Avoid nonfree software when possible

Yes, it's better to leave this guide and spend some time searching (or maybe even creating) alternatives to an application you wanted to package because:

Packaging nonfree software is often messy and often against The Arch Way

It is better to support software that is owned by us all than software that is owned by a company

It is better to support software that is actively maintained

It is better to support software that can be fixed if just one person out of millions care enough

Use open source variants where possible

Many commercial games (some are listed in this Wiki) have open source engines and many old games can be played with emulators such as ScummVM. Using open source engines together with the original game assets gives users access to bug fixes and eliminates several issues caused by binary packages.

Keep it simple

If the packaging of some program requires more effort and hacks than buying and using the original version - do the simplest thing, it is Arch!

Package Naming

Before choosing a name on your own, search in AUR for existing versions of the software you want to package. Try to use established naming conversion (e.g. do not create something like gish-hbAUR when there are already aquaria-hib-hgAUR, penumbra-overture-hibAUR and uplink-hibAUR). Use suffix -binalways unless you are sure there will never be source-based package – its creator would have to ask you (or in worst case TUs) to orphan existing package for him and you both will end up with PKGBUILDs cluttered with additional replases and conflicts.

File placement

Again, analyze existing packages (if present) and decide whether or not you want to conflict with them. Do not place things under /opt unless you want to use some ugly hacks like giving ownership root:games to the package directory (so users in group games running the game can write files in the game's own folder).

Missing files

For most commercial games there is no way to (legally) download game files, which is the preferable way to get them for normal packages. Even when it is possible to download files after providing a password (like with all Humble Indie Bundle games) asking user for this password and downloading somewhere in build function is not recommended for a variety of reasons (for example, the user may have no Internet access but have all files downloaded and stored locally). The following options should be considered:

There is only one way to obtain files

Software is distributed in archive/installer

Add the required file to sources array:

sources=(... "originalname::file://originalname")

This way the link to file in AUR web interface will look different from names of files included in source tarball.

Add following comment on package page:

Need archive/installer to work.

and explain the details in PKGBUILD source.

Software is distributed on compact-disk

Add installer script and .install file to package contents, like in package tsukihime-enAUR.

There are several ways to obtain files

Copying files from disk / downloading from Net / getting from archive during build phase may look like a good idea but it is not recommended because it limits the user's possibilities and makes package installation interactive (which is generally discouraged and just annoying). Again, a good installer script and .install file can work instead.

Few examples of various strategies for obtaining files required for package:

Advanced topics

Getting icons for .desktop files

Proprietary software often have no separate icon files, so there is nothing to use in .desktop file creation. Happily .ico files can be easily extracted from executables with programs from icoutils package. You can even do it on fly during build phase (example can be found in sugarsdelightAUR).

Unpacking

Many proprietary programs are shipped in nasty installers which sometimes do not even run in Wine. Following tools may be of some help: